How to reproduce:

• Summon a Zombie Villager with armor and/or weapons:
  /summon Zombie ~ ~ ~ {IsVillager:1b,ArmorItems:[{id:diamond_boots},{id:diamond_leggings},{id:diamond_chestplate},{id:diamond_helmet}],HandItems:[{id:diamond_sword},{id:diamond_sword}]}
• Throw a splash potion of weakness on it, and right-click on it with a regular golden apple (curing the Zombie Villager), and wait.
  Alternate, faster method: /entitydata @e[type=Zombie,c=1] {ConversionTime:1}
• When the zombie villager has been cured, the villager that comes forth out of it does not have any ArmorItems or HandItems NBTTagLists ({ArmorItems:[0:{},1:{},2:{},3:{}],HandItems:[0:{},1:{}]})